Propeller



P. C. HEWITT.

PROPELLER.

APPLICATION men JUNE 14. 1919.

Patented May 17, 1921.

INVENTOR JAMATTORNEYS aff lllllll self-sustaining,

PETER COOPER HEWITT, 0F RINGWOOD MANOR, NEW JERSEY.

PROPELLEB.

To all whom, it may concern:

Be it known that 1, PETER COOPER HEWITT, a citizen of the United States,residing at Ringwood Manor, Passaic county, New Jersey, and whosepost-oflice address is 18 East 33rd street, in the city, county, andState of New York, have invented certain new and useful Improvements inPropellers, of which the following is a specification.

My invention relates to propellers, more particularly to propellers foruse in flying machines or the like. The principal object of theinvention is to eliminate the movement that produces chattering of thepropeller blades when not'sufficiently rigid to resist as the propellerrotates in the air.

While'the location of the center of pressure or thrust on a propellerblade by the air or other fluid medium in which the propeller rotatesdepends upon various factors, such for example as the pitch angle or theangle of incidence, and the form of the blade, it is for the moreapproved forms of blades having the usual pitch angles a considerabledistance forwardly line of the blade. The ordinary solid blade, such asthe well known aeroplane propeller blade made of wood, has its center ofstrength and accordingly its center of support to the rear of the centerof pressure or thrust of the blade. There is accordingly in operation atorsion on the blade tending to increase the pitch angle or angle ofincidence, and the result with light blades in usual conditions of useis a chattering of the blade and a tendency to increase the pitch whenit should be decreased, especially when it is moving at a high velocity.

I obviate these objections by providing a propeller with blades, thecenter of support of which is forwardly of the center of pressure of theblades, the blades being, as it were, pulled rather than pushed throughthe air.

The accompanying drawing forming a part of this specification shows oneembodiment of my invention applied to an ordinary form of propeller inwhich the blades are or in other words, supported from the hub of thepropeller, or at their inner ends, entirely because of the strengththereof and without additional external supportin means.

In t e drawings, Figure 1 is a face view of said embodiment of theinvention.

Fig. 2 is a side view of the same.

Specification of Letters Patent.

and

of the longitudinal center PatentedMay 17,1921.

Application filed June 14, 1919. Serial No. 304,191.

Fig. 3 is a diagrammatic view of the same,

showing various sections of the propeller blades.

Fig. 4 is a fragmentary sectional view on a larger scale, taken on line4-4 of Fig. 2 withthe outer walls of the propeller omitted.

Fig. 5 1s a sectional view of the hub of the propeller taken on line 5-5of Fig. 4;- and Fig. 6 is a sectional view of the same taken on line 6-6 of Fig. 5.

The propeller shown comprises a hub 1, and two blades, each having aninternal supporting and reinforcing member 2, and a forward wall 3 andrear wall 4 incasing said member. All parts of the blades, as shown, aremade of sheet metal, the members 2 being circular in section and conicalin shape outer edges and likewise secured to the reinforcing members 2throughout the length'of the latter in any suitable manner, as bywelding. Each of the sheets comprising the outer walls of the propellerblades may ex- A tend integrally from one tip of the propeller to theopposite tip, being. secured intermediate -its ends to the hub 1. Tothis end the hub, asshown, is provided at its upper and lower edges withoutwardly directed flanges, 8, 9, 10 and 11, to which are secured plates12 and 14, the plate 12 being secured, as by welding to the flanges 8and 10 on one side of the hub, and the plate 14 to the flanges 9 and 11on the opposite side of the hub. The intermediate portions of the sheetscomprising the outer walls 3 and 4 The members 2, al-

sof

bear flat against the outer faces of the plates 12 and 14 respectivelyand are secured thereto in any suitable manner as by spot welding. Bycontinuous and integral from the tip of blade to the tip of the oppositeblade, centrifugal force acting on each wall toone side of the hub isbalanced by the centrifugal force acting on the same to the oppositeside of the hub.

making the walls 3 and 4 the For adding additional strength to thepropeller and to securely hold the reinforcing members 2 in positionupon the hub,

strips or straps 16 and 17 of suitable mabe secured, as by .welding toopposite sides of said memterial, such as steel, may

bers adjacent their inner ends, so as to connect said members. In orderto hold the walls 3 and 4 in their proper relationship. to each otherrearwardly of the members 2, suitable reinforcing means, such as thechannel-shaped member 18 and 19,

{of suitable materia secured as by welding between said walls.

, such as steel, may be By reason of the gradually increasingcross-section of the reinforcing and supporting members 2 from theirouter toward their inner ends, the strength of said members and of theblades increases toward the axis of the propeller and with the increaseof' outer walls of the blades may be made of the same material fromone-thousandth of an inch to one-hundredth of an inch thick, thethickness of the outer walls being'preferably considerably less than thelast-mentioned amount. With this construction, 'it is evident that thecenter of strength and support of the blade will be determined by thelocation of the members 2 and will be substantially along thelongitudinal center lines of said members. The hub of the propeller maybe of wrought steel although one of. the high tensile strengthaluminumalloys recently produced may be more a'd vantageous.

Referring to Fig. 3, the sections of the blades are shown in a wellknown manner so as to indicate not only the shape of the blades, butalso the pitch angle or angle of incidence, the propeller shown beingone of the uniform pitch type wherein the blade angle is smallest at thetip and increases toward the hub. The distances of the sections' fromtheaxis of the propeller are represented in this figure by the distancesfrom the vertical center line to the centers of the respective circlesrepresenting the members 2. The longitudinal center line of the members2 is desirably arranged a distance to the rear of the front or leadingedge of the blade equal to not more than thirty per cent. (30%) of thewidth of. the blade. This is a substantial distance forwardly of thecenter of pressure of the blade with the form of blade shown. Ingeneral, the center of support should beforwardly of the center ofpressure. With the usual.

blade forms the center of pressure does notproapproach any closer to theforward or leading edge of the blade than to a line arranged to the rearof said edge a distance equal to about twenty (20) or thirty (30) percent. of the width of the blade. When mention is made herein to theposition of the reinforcing and supporting members 2, the position ofthe axis or center of strength of the said members is generally to beunderstood. The position of the center of support will, of course, haveto be determined to best suit the requirements of any given case.

While I have shown one form of my in vention, it is to be understoodthat I am not to be restricted to this form and that modificationswithin the scope of the appended claims may be made in the specificdevice herein shown without departing from the spirit of my invention.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. A propeller having a hollow self-sustaining blade, the center ofsupport of which is forwardly of the center of pressure of the blade.

2. 'A propeller blade, the center of strength of which is forwardly ofthe center of pressure of the blade, the blade being of increasingstrength from the outer toward the inner end thereof.

3. A propeller blade having an internal reinforcing member arrangedforwardly of the longitudinal center of the blade and of increasingstrength from its outer end toward its inner end.

4. A propeller blade having an internal reinforcing member arrangedforwardly of. the center of pressure of the blade and of increasingstrength from its outer end toward its inner end.

5. A propeller blade having a tapered reinforcing member of sheetmaterial extending longitudinally thereof and arranged throughout thelength of the blade forwardly of the center of pressure of the blade.

6. A propeller blade having a tapered internal reinforcing member ofcurved cross section extending longitudinally thereof and arrangedthroughout the length of the blade forwardly of the center of pressureof the blade.

7. A propeller blade having an internal reinforcing member extendinglongitudinally thereof and arranged throughout the length of the bladeforwardly of the center of pressure of the blade, said reinforcingmember being of increasing strength from its outer end toward its innerend.

8 A propeller blade comprising an outer casing of sheet'material and .aninternal reinforclng member extendin longitudinally of sald casing andarranged forwardly of the center of pressure of the blade, saidreinforcblade, said reinforcing ing member being of increasing strength'from its outer end toward its inner end.

9. A propeller having a self-sustaining blade comprising an outer casingof sheet material and an internal reinforcing member of sheet materialextending longitudi-,

nally of said casing and arranged forwardly of the center of pressure ofthe blade.

' 10. A propeller having a self-sustaining blade comprising an outercasingof sheet material and an internal reinforcing member of strongersheet material extending longitudinall of said casing and arrangedforwardly o the center of pressure of the blade.

11. A pro eller having a self-sustaining blade comprising an outercasing of sheet material and an internal reinforcing member of strongersheet material extending longitudinally of said casing and arrangedforwardly of the center of thrust of the increased cross-section itsinner end.

12. A propeller comprising a hub and a hollow blade extending outwardlydirectly therefrom, said blade being provided with a reinforcing member.connected to said hub and arranged forwardly of the center of pressureof the blade.

I 13. A propeller haying a hub andblades carried by said hub, saidblades comprising outer walls which extend integrally from member beingof rom its outer toward of the propeller and are 'f orme'd o f said hub,and a reinforcing member for the I.

blade also connected with said hub. and arranged forwardly of the centerof pressure of the blade.

15. A propeller havinga hub and ablade carried by said hub, said bladecomprising outer walls of sheet material connected with said hub, and areinforcing member for the blade also connected with said hub andarrangedforwardl-y of the center of pressure of the blade, said memberbeing of increasing strength from its outer toward its inner end. 16. Apropeller having a hub and a blade carried by said hub, said bladecomprising outer walls of sheet material connected with said hub, areinforcing member for the blade also connected with said hub andarranged forwardly of the center of pressure of the blade, and meansreinforcing said 'walls rearwar y of said member.

In testimony whereof, I have signed my name to this specification. 7PETER COOPER HEWITT.

